This invention relates in general to air or gas cylinders which have main pistons which move backwardly and forwardly to control admission of air and to a new and useful air cylinder having a main piston which includes means for damping its end movement to an end position.
Such an air cylinder has been described in a reprint of pages 33 ff from the Blue TR-Series, No. 26, with the title "Pneumatic and Hydropneumatic Control Technique", 1976, "Technische Rundschaue", published by Hallwag, Switzerland. In this air cylinder, a smooth braking of the moved masses is obtained by plunging a damping piston associated with the working piston into a damping bore at the end of the piston motion, whereby the vent hole which is provided at the end of the damping bore is closed. Now, the air must escape through another vent provided adjacent the end portion of the cylinder space accommodating the working piston and through a throttling valve connected thereto. Since only a limited air volume can pass through this throttling valve per unit of time, a back pressure builds up by which the piston motion is braked and the piston is prevented from butting hard against the end wall of the cylinder space.
With large masses and/or high speeds, the braking back pressure upstream of the throttling valve may increase to a multiple of the working pressure at the other side of the piston. Then, the working piston rebounds from the formed air cushion. This undesirable effect may be reduced by extending and/or enlarging the cylinder, yet can never be eliminated. Further this augmentation in size is unpracticable under limited space conditions.